The Kinect is No Longer Mandatory for the Xbox One to Operate (But Will Still Come With One)

In a AMA on IGN with Marc Whitten, Chief Xbox One Platform Architect stated,

You have the ability to completely turn the sensor off in your settings. When in this mode, the sensor is not collecting any information. Any functionality that relies on voice, video, gesture or more won't work. We still support using it for IR blasting in this mode. You can turn the sensor back on at any time through settings, and if you enter into a required Kinect experience (like Kinect Sports Rivals for instance), you'll get a message asking if you want to turn the sensor back on in order to continue.